The goal of the proposed research is to design and synthesize cyclic sulfur-containing compounds that will be chelating agents for lead and mercury ions. By model-building in a computer, derivatives of the enniatin antibiotics, of the "crown ethers" and of cyclohexaamylose will be examined for their ability to provide the geometry required of a lead and/or mercury chelator. The most promising compounds will be synthesized and tested for their ability to chelate lead and mercury and to remove these ions from biological tissues.